Digital mic shrunk to 1 mm

PORTLAND, Ore.  Micro-electromechanical systems (MEMS) tapped the scalability of CMOS processing this week when the world's smallest digital microphone was shrunk even smaller—down to a single millimeter square. Akustica heralded its $2 digital microphone as the sibling of the world's smallest analog mic, which it announced earlier this year—both cast on a die 1 mm square.

Akustica's portfolio of single-chip mics is founded on the principle of CMOS scalability—both the transducer and the electronics are fabricated simultaneously on the same die using standard processing. The smallest digital microphone was designed to be the same size as the analog mic by scaling down the analog diaphragm and optimizing its circuits, then using the saved space to house analog-to-digital converters.

So far Akustica's digital microphones have been most successful in digital appliances where it would be a nuisance to use analog mics. They use single-wire pulse-density modulation encoding that can be shared by two chips for stereo or for noise-canceling or beam-steering applications.

Digital appliances using Akustica's first digital microphone chip include laptop computers, camera modules, voice-over-IP handsets and voice-enabled headsets. The company claims to be courting the lucrative mobile phone market with both its analog and digital microphones.